Absorbent articles for absorption of proteinaceous or serous body fluids such as menses blood, plasma, vaginal secretions, mucus or milk are well known in the art, and typically comprise feminine hygiene articles such as sanitary napkins, panty liners, tampons, and interlabial devices, as well as wound dressings, breast pads or the like. The purpose of such articles is to absorb and retain said body fluids. When considering in particular sanitary napkins and pantiliners, these articles typically comprise a liquid-pervious topsheet as wearer-facing layer, a liquid-impervious backsheet as garment-facing layer and an absorbent core between topsheet and backsheet. The body fluids are acquired through the topsheet and subsequently stored in the absorbent core. The backsheet prevents the absorbed fluids from wetting the wearer's garment.
It is also widely known in the art that it is beneficial for the absorption and retention characteristics of absorbent articles when portions of the article, typically the absorbent core, comprise superabsorbent materials, such as absorbent gelling materials (AGM), usually in finely dispersed form, e.g. typically in particulate form. Conventional superabsorbent materials known in the art for use in absorbent articles typically comprise water-insoluble, water-swellable, hydrogel-forming crosslinked absorbent polymers which are capable of absorbing large quantities of liquids and of retaining such absorbed liquids under moderate pressure. In general, absorbent articles comprising conventional absorbent gelling materials commonly have good absorption and retention characteristics to water and urine; however, there still remains room for improvement for absorption and retention towards certain liquids. In particular, proteinaceous or serous body fluids such as typically menses, blood, plasma, vaginal secretions, mucus or milk, are particularly difficult to be effectively absorbed and retained into absorbent articles containing conventional superabsorbent materials since said materials do not show enough absorption and retention characteristics towards said proteinaceous or serous body fluids.
Such not optimal absorption and retention are mainly caused by poor permeability of conventional superabsorbent materials towards such proteinaceous or serous body fluids, in turn due to the viscosity and/or to the complex nature of the fluids. For example, plasma, blood and menses components, including red cells, white cells, soluble proteins, cellular debris and mucus, slow down the absorption of these fluids by conventional superabsorbents. Because these fluids comprise many complex components, and are often typically rather thick, absorption into conventional superabsorbent polymers is difficult. This translates into a slower initial uptake rate of the fluid into the superabsorbent material, which can result in a lower final absorption and retention capacity if gel blocking occurs before the superabsorbent material is fully swollen.
Attempts to increase the absorption and retention capacity of superabsorbent materials for proteinaceous or serous fluids, such as blood or menses, have led for example to chemical modification of these superabsorbent materials, such as by differential crosslinking between surface and bulk of the particle, or treatment with additives, for example to improve wettability with blood by surface treatment of particulate absorbent materials using particular compounds, as disclosed in U.S. Pat. No. 4,190,563. Alternatively, or in combination, morphological modifications of the superabsorbent materials are also known in the art, for example adopting preferred shapes or dimensions for the particles.
However, although such known approaches have achieved some success in absorption and retention of proteinaceous or serous body fluids by absorbent articles comprising superabsorbent materials, they are associated to several undesirable processing and consumer use concerns. Provision of chemically and/or morphologically modified superabsorbent materials certainly adds complexity, and cost, to the production process for the manufacture of absorbent articles for absorption of proteinaceous or serous body fluids. Moreover, chemically modified superabsorbent materials can loose effectiveness during use, for example a surface coated additive can be washed away from the superabsorbent material by succeeding applications of fluid.
Consequently, there remains a need for further improvements in absorbent articles for absorption of proteinaceous or serous body fluids, such as for example sanitary napkins, which comprise polymeric materials typically in particulate form and have increased fluid absorption and retention capacity, particularly a high intake rate for such body fluids. Additionally, it would be beneficial if a reduced amount of polymeric material as compared to conventional products could be used to achieve said results.